Field of the Invention
The present invention relates to an oil seal which is one kind of a sealing device according to a seal technology. The oil seal according to the present invention is used, for example, an automobile (engine) relevant field, or is used in a general industrial machinery field.
Description of the Conventional Art
An oil seal using a fabric 51 as a dust lip has been conventionally known as shown in FIG. 4, and the oil seal is used, for example, for sealing around a crank shaft in a field of an automobile engine (a diesel engine).
In this prior art, an initial inner diameter (an inner diameter before insertion of a slinger 52) d1 of the fabric 51 is set to be smaller than an outer diameter d2 of a fabric sliding portion in the slinger 52, whereby the fabric 51 has a fastening margin. The fabric 51 is structured such that the fabric 51 is expanded along the slinger 52 when the slinger 52 is inserted, thereby securing a contact width with the slinger 52.
Therefore, since the fastening margin of the fabric 51 is set great so that the fabric 51 can be uniformly expanded circumferentially, and since an elongation load of the fabric 51 itself is high and a tense force becomes high, a sliding torque of the fabric is high, thereby preventing an improvement of fuel efficiency.
Further, since the fabric 51 has a breathability, the fabric 51 has the following advantages and disadvantages.